Neisseria meningitidis (meningococcus) is a Gram negative bacterium frequently isolated from the human upper respiratory tract. It occasionally causes invasive bacterial diseases such as bacteremia and meningitis. The incidence of meningococcal disease shows geographical seasonal and annual differences (Schwartz, B., Moore, P. S., Broome, C. V.; Clin. Microbiol. Rev. 2 (Supplement), S18-S24, 1989). Most disease in temperate countries is due to strains of serogroup B, and varies in incidence from 1-10/100,000/year total population sometimes reaching higher values (Kaczmarski, E. B. (1997), Commun. Dis. Rep. Rev. 7: R55-9, 1995; Scholten, R. J. P. M., Bijlmer, H. A., Poolman, J. T. et al. Clin. Infect. Dis. 16: 237-246, 1993; Cruz, C., Pavez, G., Aguilar, E., et al. Epidemiol. Infect 105: 119-126, 1990).
Epidemics dominated by serogroup A meningococci mostly in central Africa, are encountered, sometimes reaching levels up to 1000/100,000/year (Schwartz, B., Moore, P. S., Broome, C. V. Clin. Microbiol. Rev. 2 (Supplement), S18-S24, 1989). Nearly all cases as a whole of meningococcal disease are caused by serogroup A, B, C, W-135 and Y meningococci and a tetravalent A, C, W-135, Y polysaccharide vaccine is available (Armand, J., Arminjon, F., Mynard, M. C., Lafaix, C., J. Biol. Stand. 10: 335-339, 1982).
The polysaccharide vaccines are currently being improved by way of chemical conjugating them to carrier proteins (Lieberman, J. M., Chiu, S. S., Wong, V. K., et al. JAMA 275: 1499-1503, 1996).
A serogroup B vaccine is not available, since the B capsular polysaccharide was found to be nonimmunogenic, most likely because it shares structural similarity to host components (Wyle, F. A., Artenstein, M. S., Brandt, M. L. et al. J. Infect. Dis. 126: 514-522, 1972; Finne, J. M., Leinonen, M., Mäkelä, P. M. Lancet ii.: 355-357, 1983).
For many years efforts have been initiated and carried out to develop meningococcal outer membrane based vaccines (de Moraes, J. C., Perkins, B., Camargo, M. C. et al. Lancet 340: 1074-1078, 1992; Bjune, G., Hoiby, E. A. Gronnesby, J. K. et al. 338: 1093-1096, 1991). Such vaccines have demonstrated efficcacies from 57%-85% in older children (>4 years) and adolescents, but none of them has demonstrated no significant efficacies in younger children/adults. These efficacies were further restricted to certain defined Nm strains, i.e. to the strain used to make the vaccine, and to related strains (e.g. of same electrophoretic type), without providing an efficient protection against most of the existing Nm strains. Such vaccines does notably not provide an efficient protection against a wide range of Nm strains, such as every strain of at least one defined serogroup (such as serogroup B).
The frequency of Neisseria meningitidis infections has risen dramatically in the past few decades. This has been attributed to the emergence of multiply antibiotic resistant strains and an increasing population of people with weakened immune systems. It is no longer uncommon to isolate Neisseria meningitidis strains that are resistant to some or all of the standard antibiotics. This phenomenon has created an unmet medical need and demand for new anti-microbial agents, vaccines, drug screening methods, and diagnostic tests for this organism.